Modern conventional agricultural combine harvesters or “combines” utilize removable and interchangeable attachments called “headers” or “heads” which are adapted for harvesting different types of crops. An example of a conventional combine 10 is shown in FIGS. 1 and 2 with a conventional header attachment 20 used for harvesting corn (i.e., a “cornhead” or “cornheader”). The conventional cornheader 20 includes a plurality of conical crop divider points 22 (“points” or “snouts”) which extend forwardly and diverge rearwardly. Row unit assemblies 30 are disposed between the adjacent points where the rearwardly diverging points 22 nearly converge. In FIG. 1, a cornhead 20 is illustrated with twelve row unit assemblies 30 (i.e., a 12-row cornhead) but it should be understood that cornhead sizes typically range from four rows to twenty-four rows or more.
As illustrated in FIG. 3, during harvesting operations, the combine 10 is positioned with the points 22 of the cornhead 20 positioned between adjacent corn rows 12 and below the ears 14 on the cornstalks 16. It should be appreciated that as the combine 10 drives forwardly through the field as indicated by the arrow 18 in FIG. 2, the conical, rearwardly diverging shape of the points 22 causes the cornstalks 16 within each row 12 to be guided and directed into the row unit assemblies 30 between the adjacent points 22. As explained in more detail below, the row unit assemblies 30 separate the ears 14 from the cornstalks 16 and convey the separated ears toward the cross-auger 24. The cross-auger 24 augers the separated ears 14 toward the opening 27 of the feederhouse 26 in the middle of the cornheader 20. The feederhouse 26 conveys the ears 14 into the interior of the combine where the corn kernels are separated from the corncob. The separated kernels then pass over a series of screens which separates unwanted crop material and other residue from the kernels. The clean grain is then carried by elevators to a clean grain holding tank while the corncobs, leaves, husks and cornstalks which entered the combine are chopped and discharged through the rear of the combine and mix with the cornstalks that pass under the combine.
Referring to FIGS. 4-6, each row unit 20 includes a pair gathering chains 32, 34 with outwardly extending lugs 36. The gathering chains 32, 34 extend around drive sprockets 38 and idler sprockets 39 (FIG. 5). Rotation of the drive sprockets 38 causes the gathering chains 32, 34 to rotate in adjacent parallel paths such that as the combine 10 drives forwardly through the field, the outwardly extending lugs 36 draw the cornstalks 16 into the row unit 30. Below the rotating gathering chains is a pair of spaced stripper plates 40, 42. The stripper plates 40, 42 are spaced sufficiently apart to define a gap 44 between them which is sufficiently wide to permit the corn stalks 16 to enter but which is sufficiently narrow so that the corn ears 14 cannot pass through. A pair of rapidly rotating stalk rolls 50, 52 are positioned below stripper plates 40, 42.
As best illustrated in FIG. 6, during harvesting operations, the rotating stalk rolls 50, 52 rapidly pull the corn stalks 16 downwardly through the gap 44 between the stripper plates 40, 42 such that when the corn ears 14 engage the stripper plates 40, 42, the ears 14 are pulled or stripped from the cornstalks 16. Ideally, as the stalk rolls 50, 52 rotate, the entire cornstalk 16 is pulled downwardly through the gap 44 and is returned to the field below the header 20 as the combine drives forwardly (FIG. 2). It should be appreciated that if the cornstalk snaps or breaks prior to ear separation or after ear separation such that the entire cornstalk is not pulled through the gap 44, the amount of plant material entering the feederhouse 26 will increase, requiring more horsepower and thus more fuel consumption. The stripped ears 14 which remain on the stripper plates 40, 42 after the cornstalk 16 is pulled through the gap 44 are then conveyed by the lugs 36 of the gathering chains 32, 34 upwardly and rearwardly to the cross-auger 24. The cross-auger 24 augers the ears 14 to the feederhouse 26, and the feederhouse 26 feeds the ears 14 into the interior of the combine for shelling and separating the kernels from the corncob as is known in the art.
While conventional stalk rolls generally serve their intended purpose to pull and strip the ears from the cornstalks, conventional stalks rolls do not achieve the necessary throughput of crop material when harvesting at higher speeds. Conventional stalk rolls typically have a tapered nose portion and a cylindrical body portion. The nose portion is typically fitted with auger flights while the cylindrical portion has a plurality of horizontal flutes that run parallel to the axis of the stalk roll with the flute profile co-radial with the cylindrical portion. In use, as illustrated in FIG. 6, as the stalk rolls rotate, the auger flights on the nose draw the cornstalks towards the cylindrical body. Once the cornstalk is between the cylindrical bodies of the adjacent stalk rolls the horizontal flutes crush the cornstalks and pull the cornstalks downwardly through the stripper plates 40, 42 as previously described. It has been found that the transition point between the auger flights on the nose and the horizontal flutes on the cylindrical body of the stalk roll often restricts the throughput of the cornstalks, such that the cornstalks seam to hesitate or fail to advance, or even bind, at this transition point despite the rotation of the auger flights and forward advancement of the combine. If the cornstalks stall at this transition point, the gathering chains may snap off or break off the cornstalk causing a large portion of the cornstalk to be pulled into the cornheader and fed into the combine rather than the stripped cornstalk passing under the cornheader as previously described. Additionally, if the cornstalk is snapped off prematurely or whipped around by the stalk rolls, the corn ears can be flung from the stalk and land on the ground and not be harvested.
Second, some stalk rolls do not effectively cut and crush the cornstalk, thereby leaving long sections of the cornstalk intact and not cut and crushed in more than one direction with respect to the axis of the cornstalk. These long sections decompose very slowly, limiting their potential benefit to subsequent crops. Still other stalk rolls chop and crush the cornstalks so finely, as to potentially create a negative impact on soil microbial activity which can negatively affect the next season's crop. For example, the cornstalks that are cut and crushed and pass under the cornheader, together with the unwanted corncobs, husks and leaves that passes through and are discharged by the combine, i.e., the crop residue—commonly called corn stover—has a carbon to nitrogen to ratio of 57:1. When the stover is chopped to small pieces, soil microbes will quickly work to decompose the stover. This relatively rapid decomposition forces the microbes to find additional nitrogen to go with the excess carbon to consume the stover because it contains a greater proportion of carbon to nitrogen. The soil microbes then tie up any excess nitrogen available in the soil, called immobilization, creating a deficit of nitrogen in the soil, which nitrogen deficit can extend into the next crop season thereby negatively affecting the critical early growth stages of the next season's crop. This condition may persist until the beneficial soil microbes die, decompose, and release nitrogen (mineralization) contained in their bodies, or some other source of nitrogen becomes available in the soil.
Third, some stalk rolls are not designed to crush and cut varying cornstalk diameters. For example, cornstalks have a larger diameter at their base near the root system and the diameter decreases along the length of the cornstalk toward the tassel. It is important that the entire cornstalk length be crushed and cut to the appropriate residue size to aid in decomposition.
Accordingly, there is a need for a stalk roll which allows for high throughput of plant material, which crushes the cornstalks in more than one direction and is capable of chopping cornstalks of varying diameters across the field and of varying diameters along the length of the cornstalks to aid decomposition in the field.